1. Technical Field
The present invention relates to a position measuring device and to an apparatus having such a position measuring device.
2. Background Information
From European patent disclosure EP 1 739 395 A1, a position measuring device is known for high-precision position determination of objects that are movable relative to one another. These objects can, for instance, be machine components in semiconductor production equipment whose relative position to one another must be determined.
The known position measuring device includes a scale and a scanning unit that is movable in at least one measuring direction relative to the scale. A series of different elements for high-resolution optical scanning of the scale are disposed in the scanning unit. For instance, in the scanning units of the various exemplary embodiments, a light source, an optoelectronic detector arrangement, and one or more scanning plates with grating structures and retroreflectors disposed on them are provided. For certain applications, it is possible to place the light source and the detector arrangement spatially separate from the scanning unit, in a separate signal unit. Both the focused beams of the scanning unit or the scanning plate and the partial beams of the detector arrangement that are to be detected are each delivered via waveguides. In one such variant of the known position measuring device, the scale and the scanning unit with the scanning plate are movable relative to one another. Typically, the scale is stationary and the scanning unit is movable. Between the scanning unit and the separate signal unit having the light source and the detector arrangement, a mechanical connection or mechanical coupling therefore exists, via the waveguides that are supplied. However, for high-precision applications, such a mechanical coupling of the movable scanning unit to the signal unit, which does not move with the scanning unit, can be disadvantageous and can lead to inaccuracies in the position determination.